Feature Request: Support for new .NET Solution XML (.slnx) format

[nvntuan123]

🚀 Feature Request
With the introduction of the new XML-based Solution format (.slnx) in Visual Studio 2026 Preview and .NET 8/9, I would like to request support for parsing this file type.

📝 Problem
Currently, running the tool against a .slnx file results in an error because the parser only recognizes legacy .sln or .csproj files.

Steps to reproduce:

Create a solution using the new .slnx format.

Run the tool: dotnet tool run -i MySolution.slnx

Actual Result:

"Only .sln, .csproj, .fsproj, .vbproj, and packages.config files are supported"

💡 Suggested Solution
Update the solution parser logic to recognize and parse the XML structure of .slnx files to resolve project references.

ℹ️ Additional Context
.NET version: 8.0 / 9.0 Preview

Environment: GitHub Actions (Linux)

This format is becoming standard for modern .NET projects.

[wullemsb]

It looks like that slnx is already supported. Only the console message should be updated:
Console.Error.WriteLine($"Only .sln, .slnf, .csproj, .fsproj, .vbproj, .xsproj, and packages.config files are supported");